In the prior art, recovery of high polymeric material as a solid resinous product from a high polymer latex produced a polymer powder mixed with particles of various sizes. The prior process involved coagulating the polymer latex by adding an aqueous solution of a suitable coagulating agent, such as inorganic salts, acids, and the like to the latex or, conversely, adding the latex to such aqueous solution and thereafter heating the coatulated latex to a suitable temperature. Then, resulting the coagulated latex was dehydrated and dried. However, it was inevitable that this prior process produced product comprising particles of irregular shapes, and the diameters thereof were difficult to regulate. The distribution of particle sizes was broad and the product contained large amounts of fine powder. This causes many problems, such as a large loss of product resulting from escape of the fine powder, frequent interruption of operation brought about by the plugging of passages by the fine powder, contamination of the environmental atmosphere of the operating room by the escape of the fine powder, and danger of explosion because of the emitted fine powder.
Furthermore, since it is impossible by the conventional method to obtain a polymer powder having large bulk density, expenses for packing, storing and transportation are high. Moreover, the coagulated latex produced by the conventional procedure is inferior in dehydrative properties, drying behavior, fluidity and anti-blocking. Thus, it has been necessary to provide expensive handling apparatus in all the steps following the coagulation.
In recent years, a variety of studies have been made on methods wherein a polymer latex is: (a) dispersed as fine drops into a coagulating atmosphere containing a gaseous coagulant or an aerosol spray of a liquid coagulant; (b) coagulated therein; and (c) then recovered as coagulated latex particles in substantially spherical and uniform shapes. Nevertheless, completely satisfactory results have not yet been obtained by prior art methods.
The present inventors have made a series of studies directed to a process for effectively producing substantially spherical coagulated latex particles over an extended period of time on an industrial scale. Said inventors have succeeded in providing a method for producing the desired superior coagulated latex particles more rationally and economically, in which spherical coagulated latex particles are obtained by passing drops of latex into a coagulating atmosphere in a coagulating chamber (or zone) while preventing: (a) the deposition of coagulated latex particles onto the interior surfaces of walls of said chamber, and (b) the destruction, as well as agglomeration, of the particles by allowing water, as a recovery medium, having a specific predetermined range of temperature, to flow downward on the interior surfaces of walls of said chamber while maintaining the coagulating atmosphere at the predetermined range of temperature.